Temporal changes in enzyme activities associated with ectomycorrhizas and soil from secondary deciduous dipterocarp forest fragments

Abstract

Ectomycorrhizal (ECM) fungi form a symbiotic association with host trees, functionally promoting the nutrient uptake in the hosts via their secretion of enzymes to degrade organic compounds. Because of the involvement in nutrient cycling, ECM fungi are important to the establishment of host trees and forest recovery. In Thailand, ECM fungi are mostly associated with host tree species in the Dipterocarpaceae found in deciduous dipterocarp forests (DDFs), some of which are secondary forests naturally recovering after abandonment of logging and agriculture. To determine the function of ECM fungi in secondary DDFs, temporal changes in the ECM community structure and potential activities of three enzymes involved in nitrogen, carbon, and phosphorus cycling (β-N-acetylglucosaminidase, β-glucosidase, and acid phosphatase) from ECM roots and soils were investigated in two secondary DDF fragments in the Saraburi and Nan provinces of Thailand. A total of 180 soil samples from each forest were collected at four times across the wet and dry seasons from June 2015 to May 2016. Soil moisture content, total nitrogen, organic matter, and available phosphorus contents were measured. The results showed temporal changes in the ECM fungal communities and relative enzyme activities throughout the study period, although differences between the wet and dry seasons were not detected. The enzyme profiles associated with ECM roots were significantly correlated to the ECM communities in both DDFs. Moreover, the total nitrogen and soil moisture content influenced the temporal variation of ECM and soil enzyme profiles. These findings suggest the effect of edaphic factors combined with the ECM communities on their enzyme activities in secondary DDFs in Thailand.